Fluid-insulated electrical link device

ABSTRACT

The electrical link device comprises an enclosure ( 1, 9 ) containing a fluid insulator ( 2 ), a conductive link bar ( 3 ) disposed inside the enclosure and having one end fixed in leakproof manner to an insulating elastomer sleeve ( 12 ) that passes through the wall of the enclosure in leakproof manner, the link bar ( 3 ) being connected inside the enclosure to a pluggable connection member ( 6 ) surrounded by a conductive screen ( 15 ), the elastomer sleeve ( 12 ) also including a conductive deflector ( 16 ) flush with the inside surface of the insulating sleeve at a distance from the conductive screen ( 15 ).

The present invention relates to a fluid-insulated electrical linkdevice enabling a high voltage electricity cable to be connected to ametal-clad unit or to an outdoor unit.

BACKGROUND OF THE INVENTION

Document EP-A-148 394 discloses an electrical link device for ametal-clad unit, where the device is insulated by means of a fluid suchas sulfur hexafluoride in gaseous form. The electrical link devicedescribed in that document has a conductive link bar placed inside theenclosure with one end fixed in leakproof manner to a sleeve ofinsulating resin that passes in leakproof manner through the wall of theenclosure that contains the insulating gas. The link bar extends outsidethe enclosure and is connected to a pluggable connection member disposedin the portion of the sleeve that extends outside the enclosure and thatis surrounded by a conductive screen forming a Faraday cage around thepluggable connection member.

Such an electrical link device is the seat of high levels of electricstress when it is used at very high voltage. In addition, since thatdevice does not have any electric field-distributing member, it isnecessary to provide a separate stress-reducing member which is mountedon the electricity cable prior to it being put into position, thusrequiring manipulation to be performed to avoid electric stressesappearing at the interface between the inside surface of the insulatingsleeve and the field-distributing member, which manipulations aredifficult to perform on site.

OBJECT AND SUMMARY OF THE INVENTION

The invention proposes a fluid-insulated electrical link devicecomprising an enclosure containing a fluid insulator, and a conductivelink bar disposed inside the enclosure and having one end fixed inleakproof manner to an insulating sleeve passing in leakproof mannerthrough a wall of the enclosure, the link bar being connected to apluggable connection member surrounded by a conductive screen forming aFaraday cage around the pluggable connection member, wherein thepluggable connection member is disposed inside the enclosure, and theinsulating sleeve is made of elastomer material and includes aconductive deflector flush with the inside surface of the insulatingsleeve and at a distance from the conductive screen surrounding thepluggable connection member.

The pluggable connection member is thus surrounded by the insulatingfluid contained inside the enclosure, thereby minimizing the electricstresses in the material surrounding the pluggable connection member. Inaddition, the device of the invention can be fully assembled and filledwith fluid in a workshop such that when an electricity cable is put intoplace on site, all that needs to be done is to prepare the end of thecable and engage it in the insulating sleeve so as to plug the cableconductor without any leakage from the enclosure, thus making itpossible to avoid handling the fluid on site.

In addition, the insulating sleeve of elastomer is pressed closelyagainst the outside surface of the cable because of its own elasticityand because of the pressure of the insulating fluid surrounding it,thereby minimizing the risk of faults occurring at the interface betweenthe cable and the insulating sleeve. The deflector integrated in theinsulating sleeve then performs to the full its function as an electricfield distributor inside the insulating sleeve.

In an advantageous version of the invention, the deflector extends onboth sides of the wall of the enclosure through which the insulatingsleeve passes. This minimizes the size of the link device of theinvention without harming electric field distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will appear onreading the following description of two particular and non-limitingembodiments of the invention described with reference to theaccompanying figures, in which:

FIG. 1 is a diagrammatic axial section view of the electrical linkdevice of the invention;

FIG. 2 is a cutaway fragmentary perspective view of another embodimentof the invention; and

FIG. 3 is a section view on line III—III of FIG. 2.

MORE DETAILED DESCRIPTION

With reference to FIG. 1, the electrical link device of the invention isdescribed in the context of an outdoor unit type device, i.e. theenclosure is constituted in part by an insulator 1, e.g. an insulatormade of porcelain or of fiberglass-reinforced epoxy resin, and havingoutwardly-projecting skirts or “sheds”. At its bottom end, the insulator1 is fixed in conventional manner on a support 7 by bolts 8, and isclosed by a metal plate 9 which is fixed by means of screws 10 thatco-operate with inserts 11 embedded in the wall of the enclosure.Sealing between the plate 9 and the side wall of the insulator ispreferably ensured by an O-ring (not shown).

A metal link bar 3 extends inside the enclosure and is fixed inleakproof manner thereto. To this end, the conductive link bar 3 has acollar 4 which is fixed by means of screws to a metal insert 5 that isembedded in the wall of the insulator. Preferably, an O-ring (not shown)is disposed between the collar 4 and the metal insert 5. At its bottomend, the link bar 3 carries a pluggable connection member 6 which isrepresented diagrammatically as being in the form of a lyre-shaped clip.

The wall 9 of the enclosure has a sleeve 12 of elastomer materialpassing therethrough, e.g. a sleeve made of silicone or of EPDM, thebottom end thereof being received in leakproof manner in an opening 13through the plate 9. At its top end, the elastomer sleeve 12 is mountedin leakproof manner on the bottom end of the link bar 3, e.g. by thelink bar 3 being engaged as a force-fit in the central duct 14 of theelastomer sleeve 12.

The enclosure is filled with an insulating fluid 2 such as a gas, inparticular sulfur hexafluoride, an oil, or even a grease.

In register with the connection member 6, the elastomer sleeve 12includes a conductive screen 15 which surrounds the connection member.The conductive screen 15 is made, for example, out of elastomer that ismade to be conductive by means of carbon black. At its bottom end, theelastomer sleeve 12 has a deflector 16 which extends on both sides ofthe bottom wall 9 of the enclosure at a distance from the conductivescreen 15, with the bottom portion of the deflector 16 being flush withthe inside surface of the elastomer sleeve 12.

When an electricity cable is connected, it is initially prepared inconventional manner by a staircase of cuts that reveal in order startingfrom the end: the conductor of the cable; the insulation of the cable;and the shielding screen of the cable. The end of the cable is theninserted into the duct 14 of the elastomer sleeve 12 until the conductorof the cable is plugged in the pluggable connection member 6. The end ofthe cable insulation is then in register with the conductive screen 15and the inside surface of the duct 14 is pressed against the outsidesurface of the cable insulation, while the deflector portion 16 which isflush with the inside surface of the elastomer sleeve 12 is in contactwith the screen of the cable. To ensure that contact between the insidesurface of the elastomer sleeve 12 and the various components of thecable is intimate, the cable is preferably engaged as a force-fit, orelse the sleeve 12 is maintained in a slightly expanded state by aremovable tube which is engaged in the workshop inside the duct 14 andwhich is removed after the cable has been put into place.

FIGS. 2 and 3 show another embodiment of the invention which is intendedmore particularly for a metal-clad unit, but which can also be used inan outdoor unit of the type shown in FIG. 1. In the example shown, theenclosure containing the insulating fluid is defined by the walls or bypartitions inside the unit. In this embodiment, identical numericalreferences are used to designate those parts that are similar to partsof the first embodiment, and an insulating sleeve 12 is fixed as beforeon a plate 9 forming a portion of the wall of the enclosure and ismounted for this purpose in sealed manner to another wall portion 17 bymeans of screws 19, with sealing being provided by a gasket 19.

As in the embodiment described above, the link bar 3 is engaged inleakproof manner in the insulating sleeve 12 and has a pluggableconnection member 6 at its end which is inside the sleeve 12. At itsother end (not shown), the link bar 3 is fixed in conventional manner toa bus which extends inside the unit.

In order to be able to withstand any applied longitudinal or lateralmechanical forces, in particular while the electricity cable is beingput into place or in the event of a short circuit on the line, thedevice in this embodiment has insulating reinforcement given overallreference 20 which extends around the insulating sleeve 20. Thereinforcement 20 has one end fixed to the plate 9 and an opposite endsupporting the link bar 3.

In the embodiment shown, the reinforcement 20 has three insulatingbranches 21 shaped like flying buttresses and disposed at 120° intervalsfrom one another around the axis of the sleeve 12. One end of eachbranch 21 is fixed to the plate 9 by a screw 22 engaged in an insert 23which is embedded in the resin forming the branch 21. The other end ofeach branch 21 is fixed to a metal support ring 24 by a screw 25 engagedin an insert 26 embedded in the branch 21. The support ring 24 surroundsthe link bar 3.

To avoid the metal ring 24 generating electric stress when the link rod3 has voltage applied thereto, the conductive screen 15 which extendsaround the pluggable connection member is extended outside theinsulating sleeve 12 and extends at least as far as the support ring 24.The conductive screen 15 preferably has a rounded edge 27 and is foldedover the reinforcement as shown in the figures so as to surround thesupport ring 24 and the metal parts 26 that are associated therewith.

Naturally, the invention is not limited to the embodiments described andvariants can be applied thereto without going beyond the ambit of theinvention as described by the claims. The device of the invention canalso be adapted to the application for which it is intended.

In particular, when the device is intended for mounting on a metal-cladunit, omitting the insulator 1 makes it possible to reduce the size ofthe electrical link device to a considerable extent, and consequently todecrease the overall size of the metal-clad unit in correspondingmanner.

Although the invention is described with reference to embodiments inwhich the pluggable connection member 6 is fixed to the bottom end ofthe link bar 3, it is possible to implement a cavity in said link barand fix the pluggable connection member at the end of the cavity. Theside wall of the cavity then acts as the conductive screen 15 which canbe made smaller. This serves to further reduce the overall size of thelink device of the invention. Although the pluggable connection member 6is shown as being in the form of a female member, it is also possible toprovide a male connection member in association with the link rod 3 andto provide a female connection member on the cable.

It is also possible, inside the sleeve 12, to provide a layer ofhigh-permittivity material extending between the deflector 16 and theconductive screen 15 so as to distributed the electric field uniformly.

Although the conductive screen 15 is shown as being flush with theinside surface of the insulating sleeve 12, it could equally well beembedded in the thickness thereof.

Although the reinforcement 20 is shown as being in the form of threebranches united by a support ring, it is possible to provide a greaternumber of branches, or to provide a reinforcement that is tubular,cylindrical, or conical in shape, completely surrounding the elastomersleeve and having an inside face which can be in contact with theelastomer sleeve 12. Under such circumstances, the reinforcement caneven be used as a mold for the elastomer sleeve 12.

What is claimed is:
 1. A fluid-insulated electrical link devicecomprising an enclosure (1, 9; 17, 9) containing a fluid insulator (2),and a conductive link bar (3) disposed inside the enclosure and havingone end fixed in leakproof manner to an insulating sleeve (12) passingin leakproof manner through a wall (9) of the enclosure, the link bar(3) being connected to a pluggable connection member (6) surrounded by aconductive screen (15) forming a Faraday cage around the pluggableconnection member, wherein AG the pluggable connection member (6) isdisposed inside the enclosure (1), and wherein the insulating sleeve(12) is made of elastomer material and includes a conductive deflector(16) flush with the inside surface of the insulating sleeve and at adistance from the conductive screen (15) surrounding the pluggableconnection member.
 2. An electrical link device according to claim 1,wherein the deflector (16) extends on both sides of the wall (9) of theenclosure through which the insulating sleeve (12) passes.
 3. Anelectrical link device according to claim 1, including insulatingreinforcement (20) extending around the insulating sleeve (12) andhaving one end fixed to the wall (9) of the enclosure and an oppositeend supporting the link bar (3).
 4. An electrical link device accordingto claim 3, wherein the reinforcement (20) comprises a series ofinsulating arms (21) interconnected by a support ring (24) surroundingthe link bar (3).
 5. An electrical link device according to claim 4,wherein the support ring (24) is made of metal and in that theconductive screen (20) extends at least as far as the support ring. 6.An electrical link device according to claim 5, wherein the conductivescreen (15) is folded over the reinforcement (20) so as to envelop thesupport ring (24) and the metal parts (26) associated therewith.
 7. Anelectrical link device according to claim 6, wherein the conductivescreen (15) has a rounded edge (27).
 8. An electrical link deviceaccording to claim 3, wherein the reinforcement is tubular.